This will ensure that, for example, a user who implements "hwi"
(Hawaiian), which currently has no 2-letter code, will not find his
or her data invalidated by eventual addition of a 2-letter code for
that language.

It should say:

This will ensure that, for example, a user who implements "haw"
(Hawaiian), which currently has no 2-letter code, will not find his
or her data invalidated by eventual addition of a 2-letter code for
that language.